The subject matter disclosed herein relates to a vehicle system and, more particularly, to a vehicle system with two or more batteries connected in series.
In some vehicles, a standard 12 volt alternator is connected to a 24 volt battery. This can create an undesirable condition in that alternators do not begin to produce output until they generate a higher voltage than the battery voltage. In general, a 12 volt alternator will require rotation at about 686 RPM before it generates greater than 24 volts and can begin to output a charge. This minimum engine speed for charging exceeds generally desirable idling speeds of around 600 RPM. As such, a 12 volt alternator in a 24 volt system is ineffective to charge the 24 volt battery during idling unless the idle speed is set above 686 RPM. Since setting the idle speed higher also generally entails an increase in emissions and a greater demand on fuel this is undesirable.
This problem can be addressed by using a 24 volt alternator. However, such alternators are relatively expensive and difficult to assemble. Resultantly, 24 volt alternators are not commonly selected for use in in most vehicles. Moreover, 24 volt alternators have associated resistances that greatly exceed the resistances associated with 12 volt alternators. Consequently, they tend to generate large amounts of heat that require cooling systems.